ES2387676T3 - Procedure and device to obtain nitrogen fertilizer from organic waste products - Google Patents

Abstract

Nitrogen fertilizer is produced by heating waste product to 40-90[deg]C under reduced pressure to produce gas containing carbon dioxide and ammonia, cooling gas, contacting gas with aqueous absorbent, withdrawing resulting nitrogen fertilizer and recycling unabsorbed gas. The reduced pressure is initially generated by vacuum pump and then maintained autogenously during process. An independent claim is also included for an apparatus for carrying out the process, comprising a stripper vessel (1) for heating under reduced pressure, an absorption vessel (2), a heat accumulator (3) for heat exchange, a vacuum pump (4), a hot water pump (5), a circulating pump (6) and a stirrer (7). ACTIVITY : Fertilizer. No biological data given. MECHANISM OF ACTION : None given in the source material.

Description

Procedure and device to obtain nitrogen fertilizer from organic waste products.

The invention relates to a process and a device for obtaining nitrogen fertilizer from organic waste products in liquid phase (suspension, emulsion, dissolution), as well as for sanitizing waste or reducing emissions by heat treatment using mineral additives.

Countless procedures are known for obtaining fertilizers from organic waste such as fresh and fermented liquid manure, animal feces, slurry, manure or clarification sludge, which are oriented both to the manufacture of fertilizer and also to the sanitation of Output products and reducing the emission of harmful odoriferous substances and greenhouse gases, especially ammonia.

Thus, documents DE 196 30 387 A1 and DE 101 20 372 A1 describe processes for the manufacture of fertilizer from liquid manure with a markedly reduced ammonia release, which are based on the chemical reaction of liquid manure with humus.

Document DE 43 04 342 C1 proposes a process for the manufacture of a fertilizer based on clarification sludge by mixing calcium sulfate. A procedure for obtaining a combination fertilizer by mixing liquid manure and / or excrement with plaster is indicated in DE 41 19 504 A1.

According to DE 44 44 726 C1, a fertilizer is obtained by mixing liquid manure with clay powder and solidifying the obtained mass. In document DE 196 44 613 C2 a pelletized fertilizer from liquid manure is proposed with the use of remains containing CaO from smoke gas purification facilities.

Methods such as DE 40 33 509 A1 are also known, according to which liquid organic fertilizers and hot condensed water are mixed with biogenic substances such as straw and minerals such as gypsum to give a fertilizer that can be spread and then , are subjected to a subsequent heat treatment at a temperature of 70 to 80 ° C.

Document DE 195 47 320 A1 describes a procedure and a device for the generation of high-quality fertilizer free of sterile ammonia from biological waste substances, the fermented material being heated for at least 1 hour at boiling temperature and the ammonia released and other liquid substances being extracted with steam. According to DE 42 43 918 A1, the fermented manure is cooked in a column and the vapors containing ammonia that leave are condensed in a mixing condenser with the formation of ammonia salts.

In US Patent No. 4,076,515, a multi-stage process for the separation of ammonia during wastewater treatment by the addition of alkali is described. In the first stage, CO2 and CH4 are removed from the sewage by anaerobic digestion. The NH3 released after discharge from the digester at a subsequent stage by the addition of alkali is expelled as a gas by reducing the pressure and / or increasing the temperature and can be transformed, by transformation with acids, for example sulfuric acid, in ammonia salts, without at the same time a pure inorganic nitrogen fertilizer can be manufactured at the same time. Only an enrichment of the nitrogen content was achieved in the treated sludge from 1-2% to 10%. The procedure represented is complex and, because of the use of corrosive and poisonous chemicals, delicate from a sanitary point of view and harmful to the environment.

All the procedures mentioned above are not profitable and only incompletely achieve the objectives of the process according to the invention. The procedures that come to a fertilizer with the addition of industrial waste with additives, have to dry it and make it complex. The procedures that emit ammonia at the boiling temperature have to solve the non-simple task of condensing hot condensed water and removing the water.

The aim of the invention is the reduction of the emissions of organic waste, for example liquid manure, with the simultaneous manufacture of a high-quality nitrogen fertilizer and the transformation of discharges, especially biogas installations, into a non-turbid water. hygienically harmless contaminant through a cost-effective and technically simple procedure. The invention raised in particular the problem of providing a simple but efficient process which functions without the addition of acids or bases to the residual product to be treated and which, in addition, exceeds the known procedures in terms of performance.

According to the invention this is achieved by a process with the use of organic waste products in liquid phase (suspension, emulsion, dissolution) by heat treatment with the use of mineral additives, in which the residual product, without the addition of such chemicals as acids or lyes, it is heated to

temperatures between 40ºC and 90ºC, the pressure is evacuated at the first time up to 10 to 30 kPa and then the pressure is increased up to 40 to 80 kPa, without perceiving perceivable amounts of water, the gas that escapes at the same time , which contains carbon dioxide and ammonia, is refrigerated and an aqueous absorption medium is introduced or made contact with it, the nitrogenous fertilizer formed at the same time is extracted and the excess gas, not absorbed and containing carbon dioxide , it is pumped back to the discharge vessel, the depression generated by a vacuum pump at the beginning of the process being maintained autogenously throughout the process.

Preferably, the excess gas, not absorbed and containing carbon dioxide, is brought back into the circulation, thanks to the fact that it is introduced

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through the residual product to be treated, or

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directly above the residual product to be treated, or

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through the gas cooling system above the residual product to be treated, or

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divided into a partial stream through the residual product and another partial stream above the residual product.

A temperature which is at least 3 and a maximum of 15 K below the temperature in the extraction vessel is suitably adjusted in the gas cooling system, while the remaining refrigeration at 40 ° C takes place at the rear .

It may be advantageous to add to the excess gas, conducted in the circulation, from outside, additionally carbon dioxide in admixture with other gases, for example from biogas installations.

It is favorable to work at a pressure of 10 to 70 kPa.

At the same time it has proved advantageous to evacuate first to 10 to 30 kPa and then increase the pressure to 40 to 80 kPa.

It has also been shown that the process is preferably suitable for the treatment of animal excreta, such as liquid manure and excrement, in the liquid phase, without being limited thereto. The effect can also be transferred to other organic industrial wastes, such as fluid manure and nitrogen-containing discharges.

As especially favorable it has been shown, in the case of using fermented liquid manure, to heat it under reduced pressure to 70 to 85 ° C.

At the same time, it may be advantageous to filter the fermented liquid manure before vacuum heat treatment. The sanitized liquid discharge manure that remains after the heat treatment can then be sprayed as turbid water, practically odorless and enriched with nitrogen compounds, in meadows and fields. Solid substances separated by filtration can be well composted.

As a particularly suitable aqueous absorption medium, a suspension of gypsum in water with a solid matter content of 10% by mass up to 50% by mass has been demonstrated. It is favorable to stir this suspension and to regularly remove from the bottom of the container the nitrogen fertilizer, which contains precipitated lime and ammonium sulfate. The fertilizer can be used either directly as diluted sludge or also, after drying, as a granulated mass or as a powder or it can be stored temporarily.

The process according to the invention combines, in the preferred variant, a degassing of the residues in a vacuum with a chemical reaction of the gases escaping in a suspension of a mineral flour. Unexpectedly, the following surprising effect was discovered at the same time: if atmospheric pressure is reduced in a container filled with fresh and fermented liquid manure or liquid manure, with moderate simultaneous heating up to 40ºC to 90ºC, the liquid escapes first carbon dioxide and, at a somewhat higher temperature, ammonia, without perceptible amounts of water being transferred. If these gases are conducted inside a mineral flour suspension, which contains calcium compounds, they react with the formation of lime and ammonia salts but in such a way that the depression is maintained and the reaction continues autogenously, when the temperature in the discharge vessel is maintained at a predetermined value.

In this way, the ammonium nitrogen can be almost completely removed, for example from a fermented liquid manure. There is a cloudy, practically odorless water that no longer emits gas but still contains mineral components of liquid manure, such as potassium and phosphate, in the form of its compounds. From the agitated suspension in the feed the finished nitrogen fertilizer can be removed which contains, in addition to ammonia salts, lime, as a concentrated suspension. It can be used without further treatment.

Since the gases introduced into the receiving container are not completely absorbed by the mineral flour suspension, they are returned back to the extraction vessel and are thus driven into the circulation.

5 An acid solution, especially a sulfuric acid solution, is also suitable as an aqueous absorption product. Likewise, a combination with a suspension of gypsum in water is also a suitable variant.

10 A strikingly better result is obtained when the gases introduced into the receiving container are brought back to the extraction vessel and are thus driven into the circulation. This conduction in the circulation of excess gas is an essential feature of the invention.

The device consists of the following essential parts: 15 - an extraction vessel for heating under depression (1)

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a receiving container for heterogeneous phase reaction (2)

20 -a heat accumulator (thermosiphon) for heat exchange (3)

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a vacuum pump (4)

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a heating water pump (5) 25 -a circulation fan (6)

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a stirrer (7)

30 - as well as known pipes, blocking organs and

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technical measuring and regulation devices, to ensure an effective circulation process,

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the device contains an additional gas refrigeration system with ascending separation column and descending refrigerator and

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additional spherical pipes and taps,

so that the circulating gas can be introduced totally or partially into the extraction vessel above the residual product, or

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through the cooling system in the feeding vessel, or

- Partially, in the extraction vessel in the residual product, the residual currents being introduced, in case of division of the circulation gas, optionally in the two remaining designated points of entry.

The procedure and the device are characterized by low investment and operating costs and avoid hazards

50 for the human being and the environment. The procedure has a minimum current consumption, since the depression is maintained in the system, when it has been generated once by the vacuum pump. The necessary processing heat is provided extensively by the heat lost from the modular plant to generate combined energy and heat (BHKW) from the previously connected biogas installation. In the preferred embodiment of the invention no other chemicals such as, for example, acids and

55 lyes. The installation required for the procedure can be operated easily and can be operated as a batch process or also continuously.

The invention is described in greater detail by the following examples and the device necessary for it is represented in greater detail in three preferred variants (shown in example 1) and 60 in two special cases (described in examples 2 and 3 ), without being limited to them. The examples do not have all the features of the invention, although they facilitate the understanding of the invention.

Examples

Example 1

Figure 1 shows, by way of example, the scheme of such a device for obtaining nitrogen fertilizer, as described in more detail in example 1.

Here they mean:

1 extraction vessel for heating under depression

2 receiving container for heterogeneous phase reaction

3 heat accumulator (thermosiphon) for heat exchange

4 vacuum pump

5 heating water pump

6 circulation fan

7 stirrer

8 heat exchanger

9 discharge supply

10 heating water outlet

11 duct for heating water return

12 duct for desorption gas

13 return gas duct

14 spherical tap

15 spherical tap

16 waste removal

17 withdrawal of nitrogen fertilizer

18 rising part of the cooling system (separation column)

19 descending part of the cooling system (refrigerator)

20-22 spherical faucets for return gas

23 tap

The installation chosen as example 1 works in batch operation. The heat accumulator (3) is formed, as an example, as a layer accumulator (thermosiphon), it serves for the temporary storage of the heat of the treated discharge for the heating of the freshly loaded liquid residual product, in the example 250 liters of fermented liquid manure (discharge). The water contained in the heat accumulator is preheated, by means of the treated discharge, and is subsequently heated, through a heat exchanger (8), with the heat lost from a modular plant to generate combined energy and heat (BHKW ), so that at the head of the accumulator there is permanently a temperature of 90 ° C.

Start-up of the batch process

The fresh discharge is introduced at point (9) in the extraction vessel (1). After the container is closed, heating by heating water takes place, which is taken directly at the head of the layer accumulator at point (10), at a temperature of approx. 80 ° C The return of the heating water is supplied back to the heat accumulator (3), through the conduit (11), by means of the heating water pump (5) and, consequently, is again stratified in the corresponding temperature zone.

When the operating temperature is reached, a pressure of 40 kPA is adjusted by means of a regulated vacuum pump (4) in the entire system, and the pressure must be lowered slowly and steadily. Once this pressure is reached, the circulation fan (6) is started, so that the extraction gas is drawn, with a defined volumetric flow of gas, from the extraction vessel (1) through the conduit (12 ) as well as return gas from the feed vessel (2) to the extraction process through the conduit (13), with the help of spherical taps 20 to 22, three preferred variants of the conduction can be chosen circuit according to the invention:

Variant A: spherical tap 21 is opened, while 20 and 22 remain closed. Then the circuit gas flows completely above the level of residual product in the extraction vessel (1).

Variant B: the spherical tap 21 remains closed, the spherical taps 20 and 22 remain partially open, so that a part of the circuit gas circulates through the residual product, while the rest is supplied to the process between the column (18) and the refrigerator (19).

Variant C: the spherical tap 20 is open, and the spherical taps 21 and 22 remain closed. Then the circuit gas flows back to the process completely in the designated center of the cooling system.

Batch process development

During the batch process the temperature and pressure in the extraction vessel (1) are maintained, by connecting and disconnecting the heating water pump (5) or the vacuum pump (4), at approx. 80 ° C and 40 to 50 kPa.

Under these conditions they are expelled from the discharge, in the course of about 2 hours, first CO2 and then ammonia, they are transformed into the circuit process and washed in the subsequently connected power.

With the mineral flour existing there, for which gypsum is used, for example, the reaction products are transformed into lime and ammonium sulfate, the particles of mineral flour and lime being kept that have not been dissolved in suspension by means of the agitator ( 7). The stirring speed must be chosen in such a way that there is no obstruction of entrances and exits because of lime that precipitates.

The mass of the ammonia expelled is approx. 850 g per batch process. These transform approx. 3.4 kg of plaster which had previously been suspended in 10 l of water.

As reaction products, approx. 2.5 kg of lime and 3.3 kg of ammonium sulfate in aqueous phase. Both substances can be used, without further treatment, as fertilizer.

Batch process stop

After extensive degassing of the discharge ammonia, the gas circulation driven by the circulation fan is disconnected. The system is ventilated.

Cooling of the treated discharge takes place because, by closing the spherical tap (14) and opening the spherical tap (15), cold water from the accumulator is now conducted in the heating circuit, which is removed at the bottom of the heat accumulator, through the heat exchanger of the extraction vessel. The heat of the treated discharge is transferred in this way to the cold water of the accumulator. The water from the heated accumulator is supplied back to the accumulator through the thermo siphon and is stratified in the corresponding temperature zone in the heat accumulator.

After cooling the treated discharge, the extraction vessel is emptied at point (16) and is available for the next filling. From the feed container, after each batch process (before the formation of the vacuum for the next process), the bottom is removed through the tap (23) and a new plaster suspension is introduced.

Example 2

The invention can also be carried out by means of the special case described in greater detail in the present example 2, which has the advantage of a somewhat simpler and faster embodiment, although it is not optimally suited for all uses.

Figure 2 shows, by way of example, the scheme of such a special device for obtaining nitrogen fertilizer.

Here they mean:

A continuous line: gas circuit A dashed line and point: heating water circuit A striped line: substance currents

1 extraction vessel for heating under depression

2 feeding vessel for heterogeneous phase reaction

3 heat accumulator (thermosiphon) for heat exchange

4 vacuum pump

5 heating water pump

6 circulation fan

7 stirrer

8 heat exchanger

9 discharge supply

10 heating water outlet

11 duct for heating water return

12 duct for extraction gas

13 return gas duct

14 spherical tap

15 spherical tap

16 waste discharge

17 discharge of nitrogen fertilizer

The installation of example 2, represented as a special case, works again in batch operation. The heat accumulator (3), which is formed by way of example as a layer accumulator (thermosiphon), serves for the temporary storage of the heat of the treated discharge for the heating of the newly introduced liquid residual product. In the example, 250 liters of fermented liquid manure (discharge) were used. The water contained in the heat accumulator is preheated by the treated discharge and is subsequently heated with the heat lost BHKW by the heat exchanger (8), so that at the head of the accumulator there is always a temperature of 90 ° C.

The start-up, development and stop of the batch process take place in the same way as example 1.

Example 3

The procedure is carried out again in batch operation according to the scheme represented in example 1, but with the following modifications represented.

The fresh discharge is introduced, in point 9, into the extraction vessel (1). After the container is closed, heating by heating water takes place, which is taken directly at the head of the heat accumulator (3) at point (10), firstly up to a temperature of 70-75 ° C. The return of the heating water is supplied back to the heat accumulator (3) through the conduit (11) by means of the heating water pump (5) and is therefore stratified again in the area of corresponding temperature.

Before reaching the operating temperature, a pressure of> 400 mbar is adjusted by means of a regulated vacuum pump (4). When the final pressure is reached, the circulation fan (6) is put into operation, so that the extraction gas is aspirated, with a defined volumetric flow of gas, from the extraction vessel (1) through the conduit (12 ) refrigerated as well as return gas, from the feed vessel (2), to the extraction vessel through the conduit (13).

During the batch process the temperature in the extraction vessel (1) is maintained constant at 75-80 ° C by connecting and disconnecting the heating water pump (5), while the pressure slowly rises to 400-500 mbar.

Under these conditions they are expelled, within approximately 2 hours, of the first CO2 discharge and then ammonia and are washed in the subsequently connected feed. The discharge contains a 2.75 kg suspension of smoke gas desulfurization installation plaster in 8 liters of water, which was provided with 2 liters of a 20% sulfuric acid. The mass of the ammonia expelled is approx. 850 g per batch process. As reaction products, approx. 2 kg of lime and 3.3 kg of aqueous phase ammonium sulfate. Both substances can be used without other subsequent treatments as fertilizers.

The particles of undissolved mineral flour and lime are kept in suspension by the agitator (7). The stirring speed must be chosen in such a way that there is no obstruction of entrances and exits because of lime that precipitates.

Claims (8)

one.

 Procedure to obtain nitrogen fertilizer from organic waste products in liquid phase, as well as to sanitize waste or reduce emissions by heat treatment using mineral additives, characterized in that the residual product is heated without the addition of chemicals, such as acids or lyes , until temperatures between 40ºC and 90ºC, simultaneously the pressure is evacuated, firstly, from 10 to 30 kPa and then, the pressure is increased from 40 to 80 kPa, without appreciable amounts of water being transferred, the gas that escapes and containing carbon dioxide and ammonia is cooled and introduced into an aqueous absorption medium or brought into contact therewith, the nitrogen fertilizer formed in this way is discharged and the excess gas not absorbed and containing carbon dioxide is conducted from back to the process, keeping the temperature in the discharge vessel at the default value of ma nera that the depression between 10 and 80kPa generated at the beginning of the process by a vacuum pump is maintained autogenously during the development of the process and the ammonium nitrogen is almost completely removed.

2.

 Method according to claim 1, characterized in that the excess gas not absorbed and containing carbon dioxide is returned to the circulation, into which it is introduced

-

through the residual product to be treated, or

-

directly above the residual product to be treated, or

-

through the gas cooling system above the residual product to be treated, or

-

divided into a partial stream through the residual product and another partial stream above the residual product.

3.

 Method according to claim 1 or 2, characterized in that a temperature is set at the front of the gas cooling system, which is at least 3 and at most 15 K lower than the temperature in the extraction vessel, while in the remaining cooling takes place at 40 ° C.

Four.

 Process according to one or more of claims 1 to 3, characterized in that carbon dioxide in admixture with other gases is additionally added to the excess gas conducted in the circulation.

5.

 Process according to one or more of claims 1 to 4, characterized in that fermented liquid manure is used as waste product and it is heated under a reduced pressure of 70 to 85 ° C.

6.

 Method according to claim 5, characterized in that the fermented liquid manure, before its vacuum heat treatment is filtered in a known manner and the sanitized discharge liquid manure formed after the heat treatment is sprayed on meadows and fields in the form of turbid water. practically odorless, enriched with nitrogen compounds, while solid substances separated by filtration are composted.

7.

 Process according to one or more of claims 1 to 6, characterized in that a solution of sulfuric acid and / or a gypsum suspension with a solid matter content between 10% by mass and 50% is used as an aqueous absorption medium. in bulk, the latter being agitated in a receiving container and the product, containing lime and precipitated ammonium sulfate, being removed from the container.

8.

 Device for obtaining nitrogen fertilizer according to one or more of claims 1 to 7, formed by the following essential parts

- an extraction vessel for heating under depression (1), -a reception container for the heterogeneous phase reaction (2), -a heat accumulator for heat exchange (3), -a vacuum pump (4), -a heating water pump (5), -a circulation fan (6), -a stirrer (7), as well as some known pipes, blocking organs and measuring and regulating devices characterized in that to ensure an effective circulation process

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the device contains an additional gas refrigeration system with a rising column (18) rising and a refrigerator (19) falling and

-

additional spherical pipes and taps (20, 21, 22),

so that the circulation gas can be introduced, 5 -totally or partially, in the extraction vessel (1) above the residual product, or -through the cooling system in the feeding vessel (2), or -partially, in the extraction vessel (1) in the residual product, the residual currents being introduced, in case of division of the circulation gas, optionally in the two remaining 10 points of entry designated.